J'accuse

If I were an attorney representing the Horman family against the United States government, accusing them of playing a role in the disappearance and murder of Charles Horman, I think I would stick to one major question:  as deeply entrenched as the U.S. was in the Chilean coup, how could an American citizen be captured and killed without U.S. knowledge, if not support?  I would point to U.S. involvement in the coup, as well as their close relationship with some of the players involved.  My approach would be to hammer continually that question:  how did this happen independent of the U.S.?